I have some carved walrus ivory from when I lived in AK that have the carvers initials on the pieces. I knew a few folks that had walrus tusks and one guy I knew had some Mammath tusks he found sticking out of the banks on some of the remote rivers he was running. I presume the mammath tusks meet the 100 year old requirement, in the Govt's eyes.
Since the Marine Mammal Protection Act of 1972, AK natives and probably certain tribes in the lower 48 have been the only entities that can legally harvest marine mammals in the US. A non native can only have a piece of walrus/narwhal ivory if it has been inscribed in some manner by a native.
When I lived in AK, Teddy Kennedy came up for a visit, and was given a raw walrus tusk. He was called on the carpet by the USFWS when he was caught trying to smuggle it out of the state, but nothing came of it. If I remember correctly, he was "enabled" by getting a native carver to put some inscription on it to make it legal for him to own and went on his way with the tusk. I'd have been fined a hefty fine, the tusk would have been confiscated and I probably would have spent some time in jail if it had been me.
